Stage production workers handle the behind-the-scenes tasks that are necessary for putting on theatrical performances. Their responsibilities include costume and set design, installing lights, rigging, sound equipment, and scenery, and set building for events in parks, stadiums, arenas, and other places. During a performance they control the lighting, sound, and various other aspects of a production that add to its impact on an audience. These technicians work in close cooperation with the stage director, lighting director, actors, and various prop people. In addition, they work directly with theater shops in the construction of sets. Others are involved in the management of the theater or production. In 2012, approximately 29,400 production and technical workers were employed in nonprofit theatres, according to the Theatre Communications Group.